A certain solution contains $4.3$ grams of salt per liter. How much salt is there in $11$ liters of the solution? Round your answer, if necessary, to the nearest tenth.
Solution: This is a density word problem. To solve it, we can use the following equation, which is the volume definition of density: ${\text{Density}}=\dfrac{{\text{Total quantity}}}{{\text{Volume}}}$ What do we know? The ${\text{density}}$ of salt in the solution is ${4.3}$ grams per liter. The ${\text{volume}}$ of the solution is ${11}$ liters. What do we need to find? The ${\text{total quantity}}$ of salt. Let's denote the total weight of salt in the solutoin as $ w$. Now we can plug ${\text{density}=4.3}$, ${\text{total quantity}=w}$, and ${\text{volume}=11}$ in the equation. $\begin{aligned} {\text{Density}}&=\dfrac{{\text{Total quantity}}}{{\text{Volume}}} \\\\ {4.3}&=\dfrac{{w}}{{11}} \\\\ {11}\cdot{4.3}&= w \\\\ 47.3&= w \end{aligned}$ There are $47.3$ grams of salt in $11$ liters of the solution.